Air conditioning systems that have belonged for quite some time to the prior art condition the air to be introduced into the passenger compartment, wherein the heat required in the heat pump mode or in the reheating mode to heat the air mass flow is taken up from different heat sources.
Generic air conditioning systems with coolant-air heat exchangers that draw the heat performance from the coolant circuit of an efficient internal combustion engine of the vehicle drive no longer achieve on the one hand in the case of low ambient temperatures, for example less than −10° C., the temperature level required for a comfortable heating of the inner compartment of the vehicle. A similar situation applies for systems in vehicles with a hybrid drive. For these vehicles the use of additional heating concepts is necessary. On the other hand heat is withdrawn from the coolant so that the internal combustion engine is operated for a longer time at low temperatures, which has a negative effect on the emissions of exhaust gas and the fuel consumption. As a result of the intermittent operation of the internal combustion engine in hybrid vehicles, during rather long trips no sufficiently high coolant temperature is reached any longer. As a consequence, the start-stop operation of the internal combustion engine is stopped. The internal combustion engine is not turned off.
In addition, there is the trend to completely electrify the drive, such as, for example, in vehicles driven by batteries or fuel cells. Here, the waste heat of the internal combustion engine is removed as a possible heat source for the heating of the air.
Moreover, the amount of energy that can be stored in the vehicle battery is less than the amount of energy that can be stored in the form of liquid fuel inside the fuel tank. Therefore, in addition, the performance required for the air conditioning of the passenger compartment of an electrically driven vehicle has a significant influence of the range of the vehicle.
Air conditioning systems for motor vehicles for a combined operation in the refrigerating system mode and the heat pump mode for heating, cooling and dehumidifying the air to be supplied to the passenger compartment and conditioned are known from the prior art.
DE 102 44 954 A1 discloses a vehicle air conditioning system with a heat exchanger of a heat pump cooling cycle in a housing for an air conditioning system. The heat exchanger serves to heat or cool air that is flowing therethrough. The housing of the air conditioning system is constructed with a bypass conduit through which air flows to a flow-off side bypassing the heat exchanger.
Likewise, air conditioning systems with heat pump operation are known in which the evaporator is operated in the refrigerating system mode as well as in the heat pump mode as evaporator and the condenser is also operated in the refrigerating system mode as well as in the heat pump mode as condenser. The air conditioning systems are controlled from the coolant circuit side and/or the air side.
FR 2 743 027 A1 teaches a vehicle air conditioning system with a traditional coolant circuit comprising only an evaporator, a compressor, a condenser, and an expansion member. The heat exchangers are arranged in separate flow conduits constructed separately from each other at least as concerns the rheology. The flow conduits comprise cross connections or bypasses. The air mass flows drawn in by blowers are conducted by opening and closing flaps and by being conducted through the bypasses in accordance with the requirements and the operating mode over the surfaces of the heat exchangers. The air mass flows are cooled and/or dehumidified or heated at this time and subsequently brought into the passenger compartment and/or into the environment.
However, no operation in the reheating mode, also designated as reheat, is possible with the air conditioning systems controlled from the air side. The air conditioning systems constructed for an additional reheating operation have a complicated coolant circuit with a plurality of components such as heat exchangers, switching valves, and expansion valves.
In the “reheat” or reheating operation the air supplied to the passenger compartment is cooled down and dehumidified at this time and subsequently the dehumidified air is slightly heated. In this operating mode the required reheating performance is usually less than the required refrigerating performance for cooling and dehumidifying the air.
The air conditioning systems known from the prior art comprise a flow conduit through which fresh air is drawn in by suction from the environment or recirculated air from the passenger compartment upstream depending on the type of air inlet operation, and conditioned and conducted downstream through an air outlet switching device into the passenger compartment. However, the air conditioning systems have no air outlet flap with which the cooled-down or heated air can be brought into the environment of the air conditioning system or at least outside of the passenger compartment.